In one study, we are analyzing a bacterial DNA repair enzyme and its gene in order to understand mechanisms of repair of damaged genes. We are testing the hypothesis that the enzyme recognizes single-stranded or distorted regions of DNA next to normal ones. In a second study, we are examining the pathway of activation of a protein that senses superoxide, a mutagen, and regulates a bacterial response to it. We are testing the hypothesis that the pathway recognizes a depletion of reducing compounds that leads to oxidation of the regulatory protein and a change in the conformation of the DNA to which it is bound.